Mechanical Behavior of 3D Printed Multiwalled Carbon Nanotube/Thermoplastic Polyurethane Nanocomposites

Author(s):  
Cameron Hohimer ◽  
Nahal Aliheidari ◽  
Changki Mo ◽  
Amir Ameli

As the soft robotics industry continues to grow, the need for new materials and simplified manufacturing techniques are essential. Of interest is the development of highly flexible strain sensors that are easily integrated into these robotic components. Current strain sensing solutions using piezoresistive materials often involve complex fabrication techniques with multiple steps. Recent work by the authors has shown that thermoplastic polyurethane/multiwall carbon nanotubes (TPU/MWCNT) has good piezoresistive behavior and can be easily fabricated into strain sensors using Fused Deposition Modeling (FDM). This work expands upon that effort to characterize the mechanical properties of FDM-printed TPU/MWCNT as a function of the FDM processing parameters. In this study, the air gap, raster orientation, and MWCNT weight percent were varied and tensile tests performed. The stress-strain behavior, modulus of elasticity, and ultimate tensile strength (UTS) are compared to assess the influence of the processing conditions. Optical microscopy was also carried out to correlate the mechanical behavior to the printed mesostructures. The results show that with increased MWCNT content, the UTS decreased by as much at 47% for 2wt.%MWCNT, while the modulus of elasticity increased by 54%, compared to those of pure TPU. The results of this work provide an understanding of the mechanical performance in relation to the print parameters and sets the base to tune the mechanical properties of printed flexible functional nanocomposites.

2020 ◽  
Vol 90 (21-22) ◽  
pp. 2399-2410 ◽  
Author(s):  
Shahbaj Kabir ◽  
Hyelim Kim ◽  
Sunhee Lee

This study has investigated the physical properties of 3D-printable shape memory thermoplastic polyurethane (SMTPU) filament and its 3D-printed sinusoidal pattern obtained by fused deposition modeling (FDM) technology. To investigate 3D filaments, thermoplastic polyurethane (TPU) and SMTPU filament were examined by conducting infrared spectroscopy, x-ray diffraction (XRD), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and a tensile test. Then, to examine the 3D-printed sinusoidal samples, a sinusoidal pattern was developed and 3D-printed. Those samples went through a three-step heating process: (a) untreated state; (b) 5 min heating at 70°C, cooling for 30 min at room temperature; and (c) a repeat of step 2. The results obtained by the three different heating processes of the 3D-printed sinusoidal samples were examined by XRD, DMTA, DSC and the tensile test to obtain the effect of heating or annealing on the structural and mechanical properties. The results show significant changes in structure, crystallinity and thermal and mechanical properties of SMTPU 3D-printed samples due to the heating steps. XRD showed the increase in crystallinity with heating. In DMTA, storage modulus, loss modulus and the tan σ peak position also changed for various heating steps. The DSC result showed that the Tg for different steps of the SMTPU 3D-printed sample remained almost the same at around 51°C. The tensile property of the TPU 3D-printed sinusoidal sample decreased in terms of both load and elongation with increased heating processes, while for the SMTPU 3D-printed sinusoidal sample, the load decreased but elongation increased about 2.5 times.


Author(s):  
Behzad Rankouhi ◽  
Fereidoon Delfanian ◽  
Robert McTaggart ◽  
Todd Letcher

The following work is presented as a preliminary study on the effects of gamma irradiation on mechanical properties of Acrylonitrile Butadiene Styrene (ABS) as an in-space 3D printing feedstock to investigate the forthcoming possibilities of this technology for future space exploration missions. 3D printed testing samples were irradiated at different dosages from 1 to 1400 kGy (1 Gray (Gy) = 1 J/kg = 100 rad) using a Cobalt-60 gamma irradiator to simulate space radiation environment. Testing samples were manufactured using Fused Deposition Modeling (FDM) with a Makerbot Replicator 2x 3D printer. The correlation between the mechanical properties of irradiated samples and accumulated radiation dosage were evaluated by a series of tensile and flexural tests. Furthermore, Shore hardness tests were conducted to evaluate changes in surface hardness of irradiated parts. Finally, results were compared with a control group of samples. Findings showed a significant decrease in mechanical performance and noticeable changes in appearance of the parts with accumulated dosage of 1000 kGy and higher. However, for dosages below 10 kGy, samples showed no significant decrease in mechanical performance or change in appearance. These results were used to predict the life of a 3D printed part on board the International Space Station (ISS), on Low Earth Orbit (LEO) satellites, in deep space and long duration missions.


Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 77
Author(s):  
Sasa Gao ◽  
Ruijuan Liu ◽  
Hua Xin ◽  
Haitao Liang ◽  
Yunfei Wang ◽  
...  

Additive manufacturing provides a novel and robust way to prepare medical product with anatomic matched geometry and tailored mechanical performance. In this study, the surface characteristics, microstructure, and mechanical properties of fused deposition modeling (FDM) prepared polyether-ether-ketone (PEEK) were systematically studied. During the FDM process, the crystal unit cell and thermal attribute of PEEK material remained unchanged, whereas the surface layer generally became more hydrophilic with an obvious reduction in surface hardness. Raster angle has a significant effect on the mechanical strength but not on the failure mechanism. In practice, FDM fabricated PEEK acted more like a laminate rather than a unified structure. Its main failure mechanism was correlated to the internal voids. The results show that horizontal infill orientation with 30° raster angle is promising for a better comprehensive mechanical performance, and the corresponding tensile, flexural, and shear strengths are (76.5 ± 1.4) MPa, (149.7 ± 3.0) MPa, and (55.5 ± 1.8) MPa, respectively. The findings of this study provide guidelines for FDM-PEEK to enable its realization in applications such as orthopedic implants.


2018 ◽  
Vol 31 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Shenglong Jiang ◽  
Guangxin Liao ◽  
Dingding Xu ◽  
Fenghua Liu ◽  
Wen Li ◽  
...  

Polyetherimide (PEI) is a kind of high-performance polymer, which possesses a high glass transition temperature ( Tg), excellent flame retardancy, low smoke generation, and good mechanical properties. In this article, PEI was applied in the fused deposition modeling (FDM)–based 3-D printing for the first time. The entire process from filament extrusion to printing was studied. It was observed that the filament orientation and nozzle temperature were closely related to the mechanical properties of printed samples. When the nozzle temperature is 370°C, the mean tensile strength of FDM printing parts can reach to 104 MPa, which is only 7% lower than that of injection molded parts. It can be seen that the 0° orientation set of samples show the highest storage modulus (2492 MPa) followed by the 45° samples, and the 90° orientation set of samples show the minimum storage modulus (1420 MPa) at room temperature. The above results indicated that this technique allows the production of parts with adequate mechanical performance, which does not need to be restricted to the production of mock-ups and prototypes. Our work broke the limitations of traditional FDM technology and expanded the types of material available for FDM to the high-temperature engineering plastics.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ali Alperen Bakır ◽  
Resul Atik ◽  
Sezer Özerinç

Purpose This paper aims to provide an overview of the recent findings of the mechanical properties of parts manufactured by fused deposition modeling (FDM). FDM has become a widely used technique for the manufacturing of thermoplastic parts. The mechanical performance of these parts under service conditions is difficult to predict due to the large number of process parameters involved. The review summarizes the current knowledge about the process-property relationships for FDM-based three-dimensional printing. Design/methodology/approach The review first discusses the effect of material selection, including pure thermoplastics and polymer-matrix composites. Second, process parameters such as nozzle temperature, raster orientation and infill ratio are discussed. Mechanisms that these parameters affect the specimen morphology are explained, and the effect of each parameter on the strength of printed parts are systematically presented. Findings Mechanical properties of FDM-produced parts strongly depend on process parameters and are usually lower than injection-molded counterparts. There is a need to understand the effect of each parameter and any synergistic effects involved better. Practical implications Through the optimization of process parameters, FDM has the potential to produce parts with strength values matching those produced by conventional methods. Further work in the field will make the FDM process more suitable for the manufacturing of load-bearing components. Originality/value This paper presents a critical assessment of the current knowledge about the mechanical properties of FDM-produced parts and suggests future research directions.


Author(s):  
Saty Dev ◽  
Rajeev Srivastava

Fused deposition modeling (FDM) technology is catching the fast global market in the real-time production of polymeric parts. Process variables highly influence the performance characteristics of FDM-generated parts, so mechanical performance is not perfect for all applications. In actual conditions, parts produced by FDM are constantly subjected to loading at different temperatures. The former studies mainly concentrated on the properties of FDM products to static loading environments. There is a scope of effective investigation on the influence of FDM processing conditions on dynamic mechanical properties using artificial intelligence (AI) based techniques. The present study focused on investigation and optimization the manufacturing process parameters to evaluate the dynamic mechanical performance of FDM-produced part. The experimental runs were obtained through central composite design in Minitab software. A DMA8000 instrument was used to test the specimens for dynamic mechanical performance. The mathematical models were developed and optimized through different approaches like response surface methodology-genetic algorithm (RSM-GA) and artificial neural network-genetic algorithm (ANN-GA). The techniques for order preference by similarity to an ideal solution (TOPSIS) is employed to obtain the best parameter settings from sets of optimized solutions. The sequential use of ANN-GA and TOPSIS methods predicted the highest values of storage modulus 1619.61 MPa and loss modulus 257.38 MPa corresponding to 68.94° raster angle, 81.48% infill density, 0.10 mm layer thickness, 237.73°C nozzle temperature and 38.97 mm/s print head speed. The confirmation tests were conducted to validate the predicted result that upscale the desired properties. The RSM-GA-TOPSIS occurred with a prediction error of 2.40% and −3.31%, corresponding to storage and loss modulus. Similarly, ANN-GA-TOPSIS shows 2.17% and 2.89% prediction error corresponding to storage and loss modulus. The experimental and analytical outcome of present study will be helpful for the designers of intricate functional parts which come under thermo-mechanical loading conditions.


2019 ◽  
Vol 25 (7) ◽  
pp. 1145-1154 ◽  
Author(s):  
Xia Gao ◽  
Daijun Zhang ◽  
Xiangning Wen ◽  
Shunxin Qi ◽  
Yunlan Su ◽  
...  

Purpose This work aims to develop a new kind of semicrystalline polymer filament and optimize its printing parameters in the fused deposition modeling process. The purpose of this work also includes producing FDM parts with good ductility. Design/methodology/approach A new kind of semicrystalline filaments composed of long-chain polyamide (PA)1012 was prepared by controlling screw speed and pulling speed carefully. The optimal printing parameters for PA1012 filaments were explored through investigating dimensional accuracy and bonding strength of FDM parts. Furthermore, the mechanical properties of PA1012 specimens were also evaluated by varying nozzle temperatures and raster angles. Findings It is found that PA1012 filaments can accommodate for FDM process under suitable printing parameters. The print quality and mechanical properties of FDM parts highly depend on nozzle temperature and bed temperature. Even though higher temperatures facilitate stronger interlayer bonding, FDM parts with excellent tensile strength were obtained at a moderate nozzle temperature. Moreover, a bed temperature well above the glass transition temperature of PA1012 can eliminate shrinkage and distortion of FDM parts. As expected, FDM parts prepared with PA1012 filaments exhibit good ductility. Originality/value Results in this work demonstrate that the PA1012 filament allows the production of FDM parts with desired mechanical performance. This indicates the potential for overcoming the dependence on amorphous thermoplastics as a feedstock in the FDM technique. This work also provides insight into the effect of materials properties on the mechanical performance of FDM-printed parts.


Author(s):  
Steffany N. Cerda-Avila ◽  
Hugo I. Medellín-Castillo ◽  
Dirk F. de Lange

The prediction of the structural performance of additive manufacturing (AM) parts has become one of the main challenges to boost the use of AM in industry. The structural properties of AM are very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. While AM experimental studies are common in the literature, a limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches, such as the finite element method (FEM); however, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication. In this paper, the analysis and numerical simulation of the structural performance of fused deposition modeling (FDM) samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and polylactic acid (PLA) material. These samples were measured and modeled in a computer-aided design (CAD) system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally, the experimental and numerical results were compared and conclusions drawn.


Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 740
Author(s):  
Wattanachai Prasong ◽  
Akira Ishigami ◽  
Supaphorn Thumsorn ◽  
Takashi Kurose ◽  
Hiroshi Ito

Poly(lactic acid) (PLA) filaments have been the most used in fused deposition modeling (FDM) 3D printing. The filaments, based on PLA, are continuing to be developed to overcome brittleness, low heat resistance, and obtain superior mechanical performance in 3D printing. From our previous study, the binary blend composites from PLA and poly(butylene adipate-co-terephthalate) (PBAT) with nano talc (PLA/PBAT/nano talc) at 70/30/10 showed an improvement in toughness and printability in FDM 3D printing. Nevertheless, interlayer adhesion, anisotropic characteristics, and heat resistance have been promoted for further application in FDM 3D printing. In this study, binary and ternary blend composites from PLA/PBAT and poly(butylene succinate) (PBS) with nano talc were prepared at a ratio of PLA 70 wt. % and blending with PBAT or PBS at 30 wt. % and nano talc at 10 wt. %. The materials were compounded via a twin-screw extruder and applied to the filament using a capillary rheometer. PLA/PBAT/PBS/nano talc blend composites were printed using FDM 3D printing. Thermal analysis, viscosity, interlayer adhesion, mechanical properties, and dimensional accuracy of binary and ternary blend composite 3D prints were investigated. The incorporation of of PBS-enhanced crystallinity of the blend composite 3D prints resulted in an improvement to mechanical properties, heat resistance, and anisotropic characteristics. Flexibility of the blend composites was obtained by presentation of PBAT. It should be noted that the core–shell morphology of the ternary blend influenced the reduction of volume shrinkage, which obtained good surface roughness and dimensional accuracy in the ternary blend composite 3D printing.


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